Happy to jump in as the founder of one of these, Sia. We build consensus using proof of work, and then we throw some smart contracts on top of the consensus system to build a secure marketplace for cloud storage.

The result so far has been really potent. On the Sia network today, raw storage (pre-redundancy) costs about $0.30 per TB. Performed intelligently, you only need about 2x redundancy, putting the total cost at less than 1/10th of Amazon glacier.

I project that as the network grows, demand will catch up to supply more and the price will settle closer to $2 / TB / Mo for raw storage.

I can answer any questions.

Check out BURST.